This invention concerns a valve of all-molded plastic construction and improvements in the design of one or more sealing means which are incorporated therein to render sealing more efficient while greatly reducing cost. Such valves may have particular application in systems for suctioning fluids from the lungs and alternatively, for oxygenating the lungs of patients requiring such treatment and as such may be made sufficiently inexpensively to be disposable.
Gate valves (often called slide valves) operate on the same basic principle. The housing or body of the valve contains one or more inlets and connected thereto, passages through the housing which conduct fluids to one or more outlets. The housing includes a recess or slot which receives the slide member or gate, often a flat rectangular or semi-circular member. The slide member contains one or more fluid passages or apertures which can be selectively aligned by reciprocation or rotation of the slide member with one or more through passages in the housing or valve body, thus controlling or limiting flow through the valve.
Attempts have been made to produce valves of this type by molding the housing and slide member of plastic, for example by injection molding. This type of manufacture obviously can produce a valve less expensively than for example, where the parts are of metal and particularly where machining and precision fitting of parts is required. However, it is difficult, if not impossible to maintain close tolerances, using present injection molding techniques, between the dimensions of the slide member and the recess in the valve housing which receives the slide member. In order to produce an efficient valve, where sealing is effected directly (without the interposition of specific sealing means) between slide member and valve housing, the difference in width between the slide member and its recess would have to be held to say, one-half thousandths of an inch (0.0005"). It is not unusual when molding valves of this type however to be unable to hold tolerances of less than plus or minus five thousandths. The use of conventional seals in such circumstances will not satisfactorily solve these wide dimensional differences, and it has been found that to attempt efficient sealing would be to introduce large frictional forces which inhibit movements of the slide member. It is one of the important aspects of the present invention to solve these inherent problems in the manufacture of molded plastic valves of this type.
In the environment in which the present invention is depicted herein, one side of the valve is connected to a source of suction and to an oxygen source, the outlet of the valve being connected to a catheter which passes into the lungs of a patient to be treated. The valve body has fluid passages therethrough which extend from the inlet openings to a single outlet, the valve body further defining a recess perpendicular thereto which receives a slide member or gate. The latter is reciprocable or rotatable and defines at least one opening which can be selectively aligned with the aforesaid fluid passages to prevent or interrupt flow to the outlet. Within the oxygenation/suctioning environment, illustrations of systems and valves of this type, may be found in U.S. Pat. Nos. 4,193,406 and 4,300,550.
A serious problem shared by these prior valve constructions is their lack of adequate sealing between slide member and fluid passage orifices which greatly impairs the efficiency of the systems incorporating them. Where, for example, fluid is suctioned from, and oxygen is alternatively provided to the lungs, it is imperative and apparent that each operation be performed as expeditiously as possible to minimize potential harm to the patient and leakage of oxygen or bacterially contaminated air to the surrounding environment. Therefore, generally speaking, one of the important aspects of the present invention is to provide improved sealing means which obviates the above difficulties and which is expected to have use in many other applications other than the disclosed oxygenation/suctioning system. The sealing construction disclosed herein (which is a laminated seal) has been used heretofore as a gasket (engines) and as a seal around aircraft canopies and exit doors and has been used to seal medicinal ampules or vials; as used herein it is a significant improvement over the foregoing applications and valve and other sealing configurations found for example in U.S. Pat. Nos. 4,089,506; 3,907,310; 4,111,440; 4,019,535; 4,465,062; 4,538,607.
As will be described, the gate valve sealing means of the invention particularly finds application in inexpensive molded plastic valves which may have to be disposable for hygienic reasons; i.e. in hospital environments. The improved seal construction significantly reduces the cost of molding the body of the valve; maintaining close tolerances to achieve effective sealing; and the cost of the plastic materials chosen for particular valve construction, while simultaneously providing greatly increased sealing efficiency.
Other improved features of the new valve construction include an improved non-contaminating valve venting system will become apparent upon examination of the detailed description and drawing.